Thermocouple tube with exposed junction



c. s. TEGGE 2,5,159

THBRMOCOUPLE TUBE WITH EXPO Filed Aug. 12, 1943 SED JUNCTIONS INVEN TOR.

CARLTON S. TEGGE atented July 13, 1948 mnmooourna TUBE urn nmosnn JUNCTION Carlton S'. Tezgafladdon Heights, N. 3., assignor to The Brown Instrument Company, Philadelphia, Pa", a corporation iii Pennsylvania Application August 12, 19M, Serial No. 498,328

6 Claims.

The present invention relates to thermocouples, and more particularly to a thermocouple assembly having an exposed hot junction, which assembly may be used in connection with a closed container under pressure, or in any other desired place.

' by this construction is objectionable.

It is an object of this invention to provide a thermocouple assembly in which the thermocouple hot junction is exposed tothe medium whose temperature is being measured. It is a further object of the invention to provide a thermocouple assembly in which a protecting tube is joined in pressure tight relation with the elements forming the thermocouple itself.

It is a further object of the invention to provide a thermocouple assembly in which all or the thermocouple but the hot junction is encased in a protecting tube with the feature that the construction is pressure tight and that the hot junction is exposed to the temperature to be measured.- Such a construction produces a thermocouple which is fast in its response to temperature changes and which may be used in places where ordinary thermocouple constructions are unsatisfactory because of the lag which is involved in measuring temperature changes.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding oithe invention, however, its advantages and specific objects obtained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of the invention.

Inthe drawings:

Figure 1 is a view, partly in section, of one form of my invention,

Figure 2 is a view, partly in section, of a modifled form or my invention, and V Figure 3 is a view, partly in section, of another modified form or my invention.

, Referring first to Figure 1 there is shown a thermocouple protecting tube i oi steel or other suitable material which is adapted to be fastened in the wall of a container or vessel by means of a threaded portion 2. The tube has attached to its left end a thermocouple head 3 in which are located the conventional terminals for the thermocouple wires and terminals by means of which the thermocouple can be connected, to a suiteble measuring instrument through the use of extension leads. The right end of the protecting tube i is cut ofi as is shown in the figure and has received in it a short tubular member t which in turn receives in it a glass or other fusible, insulating member 5. This latter member is provided with openings through which the thermocouple wires 6 and 1 may extend. The wires are joined together at the right of member 5, as shown at 8, to form the hot junction of the thermocouple and to the left of member 5 extend through suitable insulators i! to the thermocouple head 3. Insulators ii are preferably made of some ceramic and serve to separate and support the thermocouple wires in their passage through the protecting tube I.

In the making of this thermocouple assembly, the thermocouple wires ii and i are placed through suitable openings that are provided in the member 5 and this member is then placed within the bore of the tubular member 6 that is made of a metal which preferably has a coefficient of expansion substantially the same as that of the member 5. The tubular member t may he made of Kovar which is an alloy of iron, nickel and cobalt, but it may also be made of any material which has a suitable coefficient of expansion with respect to that of the glass insert 5. This assembly is then heated in a suitable furnace until the member 5 will flow into intimate contact with the wires 6 and i and with the tube 4, fusing them together, in order to make a pressure-tight seal between the various components. After this is done the tube fl is inserted in the outer end of the protecting tube i and Welded thereto as shown at Ill in order to form a pressure tight junction between the tube i and the protecting tube I.

From the above it will be seen that there is provided a thermocouple assembly in which the thermocouple wires are suitably protected but in which the hot junction itself is exposed to the medium whose temperature is being measured. By the construction that has been described a pressure tight union is obtained between each of the components of the thermocoupie assembly so that when the protecting tube is immersed in a space which is under pressure the pressure will not be lost. This provides a thermocouple which is extremely sensitive to temperature changes and which may be usedinside'of vessels under pressure.

The-construction shown in Figure 2 is adapted to perform tlie same function as that described in connection with Figure 1, but is made in a slightly different manner. In this embodiment of the invention the tube I is counter-bored to form an internal shoulder ii. Against this shoulder there is placed a ceramic member l2 through which are provided openings that snugly receive the thermocouple wires 6 and i. The member I! is held in place in the tube l by means of a suitable cement t3 which serves to make a pressure tight connection with the interior walls of the protecting tube and at the same time closely surrounds the thermocouple wires so that a pressure tight connection is also made with them. A second ceramic member I l, similar to the member I2 is inserted in the outer end of the protecting tube in order to keep the cement in place. This member also serves to compress the cement tightly against the first member l2 and against the walls of the protecting tube. In addition to supporting the wires 6 and 1, members l2 and M serve to insulate them from each other. It is noted that the member Id is held in place by the cement.

[In forming this type of thermocouple, the thermocouple wires are threaded through the members it and i i, and the member I2 is placed in position in the protecting tube I. While the members it and it are separated the proper amount of cement i3 is placed in the open end of the'tube. into the open end of the protecting tube and moved toward the left with sufficient force to compress the cement until a pressure tight joint is formed. Any suitable type of cement which is capable of forming a bond between the parts may be used, provided this cement is capable of withstanding the maximumtemperature to which the thermocouple will be subjected. It is noted that the pressure to which the thermocouple is subjected pushes the parts i2, I3 and 14 toward the shoulder H to help retain the parts of the asseinbly in position.

There is shown in Figure 3 another type of thermocouple which may be made in accordance with my invention, and which depends on another method of assembly in order to obtain the pressure tight joint. In this embodiment of the invention a washer i5 which may be made of asbestos, soft copper or other suitable material is placed against the shoulder ll formed in the protecting tube I, and a ceramic insulating member I6 is moved into the end of the protecting tube to hold this washer in place. Thereafter the thermocouple wires 6 and 1, each having placed on them beads l1 and iii of a material similar to that of which the washer I5 is formed, are threaded through openings provided in the member IS. A second ceramic insulating member I9 is then threaded on the ends of the thermocouple wires to the position shown. These members are held in place and are forced tightly toward the shoulder ll of the protecting tube by spinning over the end of the protecting tube as shown at 20. This operation will move the ceramic member l6 against the washer it with sufficient force to make a pressure tight joint between this washer and the protecting tube.. The member IE will be Thereafter a member [4 is placed I moved toward the member l6 with sufficient force IB to make a presto compress the beads I1 and sure tight Joint between these members and the wires 8 and I so that there can be no leakage around the thermocouple wires and through the members in the manner that has been described the ends of the thermocouple wires'6 and l are joined to form the hot Junction 8.

From the above description it will be seen that I have provided 'a thermocouple assembly which is so designed that a bare thermocouple-hot Junction may be exposed to the medium whose temperatureis to be measured to thus insure a highly sensitive measuring element. This construction also is so assembled that it may be inserted in a vessel under high pressure without the loss of pressure due to the insertion of the thermocouple. The construction described, furthermore, is easy to make and is inexpensive in addition to being very eflicient for its designed purpose.

While in accordance withtthe provisions of the statutes I have illustrated and described the best form of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims, and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A thermocouple assembly comprising a pair of thermocouple wires, a glass member surrounding said wires anddn intimate engagement with the same, a tube having.the same coefiicient of expansion as said glass member receiving the same and integrally fastened to the member, a

protecting tube adapted to extend through an opening and be fastened to the wall of a space whose temperature is to be measured, said protecting tube having an open end, and means to integrally attach said first mentioned tube to the open end of said'protecting tube whereby a pressure tight construction is obtained, and the thermocouple assembly serves to plug said opening.

. 2. A thermocouple assembly comprising a pair of wires joined at their hot ends to form a hot junction, a fusible insulating member surroundme said wires adjacent said hot Junction and being sealed in pressure tight relation thereto with the hot junction exposed, a cylindrical metal part surrounding and integrally attached thereto, said part having a coefficient of expansion substantially the same as that of said fusible member, a protecting tube having an open end, means to fasten said cylindrical part in the open end of said protecting tube in pressure tight relation thereto, whereby said but junction projects beyond the open end of said protecting tube and is insulated therefrom and the entire assembly may be inserted in a space under pressure without the loss of pressure therefrom.

3. A thermocouple assembly comprising a protecting tube having an open end, said tube being counterbored so that it'is provided with an internal shoulder, an insulating member received by said tube and tightly engaging said shoulder, a body of cement, acting to hold said member in said tube, a second'insulating member also received by said tube beyond the body of cement and held in place by the same, a pair'or thermocouple wires, said members having openings in l6 and I9. After the assembly is made i them through each or which said pair 0! thermocouple wires is threaded, the cement closely surrounding said wires, whereby the open end of said protecting tube is closed and the thermocouple wires are exposed beyond the end of the same.

4. A thermocouple assembly comprising an open ended protecting tube having an internal shoulder therein, a. plurality of insulating plugs received in the open end of said protecting tube, one of said plugs resting against said shoulder, a body of bonding material between each of said plugs and in intimate engagement therewith and with the interior of said protecting tube, a pair of thermocouple wires, each of said plugs being provided with openings through which said thermocouple wires pass so that they extend from the interior of said protecting tube to the exterior thereof, the outer ends of said thermocouple wires being joined to form a hot junction.

5. A thermocouple assembly comprising an open ended protecting tube provided with an internal shoulder, an annular gasket member engaging said shoulder, a pair of plugs received in said tube, one of them engaging said member, a pair of thermocouple wires, each of said plugs being provided with openings through which said wires may be passed, an enlargement on each thermocouple wire and located between said plugs, and means to force said plugs together against said enlargements and said one plug against said gasket.

6. A thermocouple assembly comprising a protecting tube formed with an. internal shoulder, a pair of thermocouple wires extending through said protecting tube, a plurality of insulating members received in said tube, each of said members being provided with openings through which said wires pass, an enlargement on each wire located between said members, means to force said members toward each other to compress said enlargements and toward said shoulder, and a gasket located between one of said members and said shoulder, said thermocouple wires being joined to make a thermocouple hot junction at a point beyond the last of said members.

CARLTON S. TEGGE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 869,668 Thwing Oct. 29, 1907 935,154 Hopkins Sept. 28, 1909 1,054,442 Nice Feb. 25, 1913 1,367,026 Drinker Feb. 1, 1921 1,422,672 Coghlan July 11, 1922 2,022,529 Townsend Nov. 26, 1935 2,137,057 Mason Nov. 15, 1938 2,218,622 Rabezzana Oct. 22, 1940 2,223,408 Dietert Dec. 3, 1940 2,258,809 Rabezzana Oct. 14, 1941 2,318,479 Gillis May 4, 1943 OTHER REFERENCES Williams, A., Trans A. S. M. E., vol. 57 (1935), p. 497. (Copy in Div. 60.)

Leeds et al., Catalog N33-162 (1937), p. 26. (Copy in Div. 60.) 

